Circuit arrangement for the control of welding voltage



July 12, 1960 H. J. A. M. JACOBS ET AL 2,945,161

CIRCUIT ARRANGEMENT FOR THE CONTRQL OF WELDING VOLTAGE Filed May 8, 1958 Ann vvvvvv AAAAAA INVENTOR HENRI JOSEPH ANTONIUS MARI JACOBS LEONARDUS FRANSISCUS VAN DE WEWEVEN LAMBERTUS WILHELMUS ROOSEN DAAL AGENT CIRCUIT ARRANGEMENT FOR THE CONTROL OF WELDING VOLTAGE Henri Joseph Antonius Marie Jacobs, Leonardus Fransiscus van de Weijdeven, and Lambertus Wilhelmus Roosendaal, all of Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed May 8, 1958, Ser. No. 733,877

Claims priority, application Netherlands June 3, 1957 4 Claims. (Cl. 315-205) The present invention relates to a circuit arrangement for producing square-wave control-voltages. More particularly, the invention relates to an arrangement for controlling resistance welding apparatus (for example, with the aid of two controllable, gas or vapor-filled, inversely parallel-connected discharge tubes). In the circuit arrangement of the present invention, provision is made of means to supply ignition pulses of the power supply frequency, preferably of a sharp waveform, to two gas or vapor-filled, direct-voltage-fed discharge tubes. The discharge tubes are included in a trigger circuit, so that when one tube ignites, the other tube extinguishes and conversely. The ignition pulses are constantly supplied to one tube and are operative at the other tube only for a desired period. The square-wave control-voltages are derived from at least one of the anode-cathode circuits of these tubes; impedances being included in said anodecathode circuits. 7 The time during which each of the two tubes is ignited is determined by the discharge time of two charged capacitors, which serve as a negative voltage source for the control-circuits of the tubes. Each capacitor is connected to the anode of one of the tubes and, via the ignition pulse source, to the control-electrode of the other tube.

Such a circuit arrangement is complicated and hence is not economical.

A materially simpler arrangement is obtained in accordance with the invention by connecting the junction of each of the capacitors with the said source via a resistor to the negative terminal of the supply voltage source of the trigger circuit.

According to another feature of the invention, the synchronous switching-on may be obtained by supplying the ignition pulses, which are operative only for a desired period of time, via a switch, which is constituted by a high-vacuum diode. The anode of the diode is connected to the control-electrode of the said other tube and the cathode is connected via a resistor to the said negative terminal. The cathode is also connected to the cathode of a controllable, gas or vapor filled, directvoltage-fed auxiliary discharge tube. The auxiliary discharge tube is included, with another auxiliary tube, in

a second trigger circuit. The use of a high-vacuum tube has the advantage that it passes current at the comparatively low voltages of the ignition pulses.

cation of the embodiment of Fig. 1.

Referring to Fig. 1 two controllable, gas or vapor filled 2,945,161 Patented July 12., 1950 discharge tubes 1 and 2 are included in known manner in a trigger circuit. A capacitor 3 is provided between the anodes which are connected to the positive terminal of the direct-voltage source 6 via resistors 4 and 5. A common cathode-resistor is designated by 7.

Each of the anodes is connected via acapacitor 8 and 9, respectively, and via the secondary windings 10 and 11 on a common core 12 of a saturated transformer to produce the ignition pulses, to the grid of the other tube. The primary winding of the transformer is omitted for the sake of simplicity. The capacitors 8 and 9 are connected, moreover, via the variable resistors 13 and 14 to the negative terminal of the source 6. Between the grid of the tube 2 and the negative terminal is arranged a switch 15, which may be'replaced by a controllable discharge tube.

If the switch 15 is closed, the ignition pulses are inoperative at the winding 11 and the tube 2 isextinguished, whereas the tube 1 is conductive due to the ignition pulses across the winding 10.

The capacitor 8 is charged rapidly to the full value of the direct-voltage source 6 via the resistor 5,'the winding 10, the grid-cathode of the tube 1 and the resistor 7, the lower coating of the capacitor, connected'to the grid, being negative. A voltage is operative at the output terminals 16 and 17 which is equal to the voltagedrop across the anode resistor 4, indicated in Fig. 3 by the line 18. This voltage may serve, for example, as

'a negative bias voltage for another controllable gas or vapor filled discharge tube; it being assumed that no welding current is supplied.

It then the switch 15 is opened, the tube 2 ignites at the instant 19 (Fig. 2) at the next-following ignition pulse across the winding 11, since the negative bias voltage across the cathode resistor 7 is not high enough to prevent it. Thus the tube 1 extinguishes, while, moreover, the negative potential at the lower coating of the capacitor 3, and hence the negative potential at the grid of the tube 1, are abruptly increased due to the great potential drop across the anode of the ignited tube-2. This negative potential is indicated in Fig. 2 at the instant 19, the voltage pulses superimposed thereon across the winding 10 being designated by 20 and the ignition characteristic of tube 1 by 21. .The capacitor 8 will discharge via the comparatively high resistor 13, the resistor 7 and the ignited tube 2, at a comparatively slow ratein accordance with the line 22 of Fig. 2 during a period of time 23, which varies with the adjusted value of the resistor 13. At the end of this period of time the tube 1 ignites again, since the ignition pulse 20 (shown as the last pulse) intersects the ignition characteristic 21. v

For the period of time 23' (see Fig. 3) no voltage is operative at the output terminals 16 and 17, since the tube 1 does not convey anode current.

In the meantime, the capacitor 9 has been charged completely and the same process is repeated at tube 2.

Referring to Fig. 3, the period of time is designated by 24, during which the tube 1 is ignited and the tube 2 is extinguished, so that the welding time is equal to the period of time 23 and the intermittent time equal to 24. The welding time and the intermittent time may be adjusted by means of the resistors 13 and 14. If desired, a control-voltage may be derived from the resistor5, the period of time of this voltage being equal to 23.

In order to determine accurately the number of welding periods and intermittent periods, the switch 15 may be replaced (see Fig. 4) by the series-connection of a highf vacuum diode 25 and a resistor 26. The cathode of the tube 25 is connected to means for controlling the conductive condition of said tube, such as the cathode of a controllable, gas or vapor filled, direct-voltage-fed auxiliary discharge tube 27. The control-circuit of the tube positive terminal, anode of said "second "tube to said positive terminal, a

27 is shown diagrammatically and designated by 28. If the tube 27 is not conductive, the ignition pulses at the winding 11 will be conducted away via the diode 25, so that the tube 2 is extinguished. If the tube 27 becomes conductive, the voltage :drop across the resistor ,261'becomes 'so large and hence the cathode of the. tube 25 positive-to such an extent-that the-diode 25 is extinguished and tube 2 is ignited.

The last-mentioned trigger circuit is, in many cases, advantageous with respect to further controhmanipulations, for example, the electrode pressure prior to and after a welding -cycle,the preheatin-gand postheating-time and so on.

While the invention has been described by means of specificexamples and in specific embodiments, -we-do not wish to be limited thereto, for obvious modifications -will occur-to thoseskilled in the art without departing from the spirit andscope of the invention.

What is claimed is:

1. A circuit arrangement comprisingfirst and second gas dischargetubes each having an anode, a cathode and a control grid, said cathodes being connected together, means for supplying a direct voltage having a positive polarity terminal and a negative polarity terminal, a first resistor connecting the anode of said first tube to said positive terminal, a second resistor connecting the anode of said second tube to said positive terminal, a third resistor connecting the common cathode connec tion to said negative terminal, means for deriving an output voltage across said first resistor, first ignition pulse supplying means, a first capacitor connected in series circuit'arrangement with said first pulse means between the control electrode of said first tube and the anode of said second tube, said first pulse source being interposed between said first capacitor and said control grid, at first variable resistor connected between a point in said series circuit arrangement interposed between said firstcapacitor arid said first pulse means and said negative terminal, second ignition pulsesupplying means, a second capacitor connected in series circuit arrangement with said second pulse means between the control-electrode of said second tube and the anode of said first tube, said second pulse source being interposed between said second capacitor and said controlgrid, a second variable resistorconnected between a point in'said last-mentioned series circuit arrangement interposed between said second capacitor and said second pulse means and said negative terminal, and means for interrupting the supply of ignition pulses to said second tube whereby'the conductive condition of each ofsaid tubes-is controlled, said tubes being alternately conductive for periods determined by the dischargetimes "of the associated first and second capacitors.

2. Aycircuit arrangement comprising first and second gas'dischargetubes each having an anode, a'cathode and a control grid, said cathodes being connected together,

means for supplying a direct voltage having a positive polarity'terminal and a negativepolarity terminal, a first resistor connectingthe'anode of said first tube to said a second resistor .connecting the third resistor connectingthe common cathode connec- 'tionto said negative terminal, means for-deriving an "output voltage across said first resistor, first ignition pulse supplying means, a first capacitor connected in series circuit arrangement with said first pulse means between the control electrode of said first tube and the anode of said second tube, said first pulse source being interposed between saidfirst capacitor and said control grid, a first variable resistor connected between a point in said series "circuit arrangement interposed between said first capacitor and said first pulse means andsaid negative terminal, second ignition pulse supplying means, a second. capacitor "connected in series circuit arrangement with said second pulse means between the control electrode of said second "tube and the anode 'OfSaldYfiI'St'tHbG, said second pulse source being interposed between said second capacitor and said control grid, a second variable resistor connected between a point in said last-mentioned series circuit arrangement interposed between said second capacitor and said second pulse means and said negative terminal, and switch means connected between a point on the connection between said second pulse source and the control electrode of said second-tube and said negative terminal for interrupting the supply of ignition pulses to said second tube whereby the conductive condition of each of said tubes is controlled, said tubes being alternately conductive for periods determined by the discharge times of the associated first and second capacitors.

3. A circuit arrangement comprising first and second discharge tubes each having an anode, a Cathode and a control grid, said cathodes being connected together, means for supplying a direct voltage having a positive polarity terminaland. a negative polarity terminal, a first resistor connecting the anode of said first tube to said positive terminal, a second resistor connecting the anode of said second tube to said positive terminal, a third resistor connecting the common cathode connection to said negative terminal, means for deriving an output voltage across said first resistor, first ignition pulse supplying means, a first capacitor connected in series circuit arrangement with said first pulse means between the control electrode of said first tube and the anode of said second tube, said first pulse source being interposed between said first capacitor and said control grid, at first variable resistor connected between a point in said series circuit arrangement interposed between said first capacitor and said first pulse means and said negative terminal, second ignition pulse supplying means, a second capacitor connected in series circuit arrangement with said second pulse means between the control electrode of said :second tube and the anode of saidfirst tube, said second pulse source beinginterposed between said second capacitor and said control grid, a second variable resistor connected between a point in said last-mentioned series circuit arrangement interposed between said second capacitor and said second pulse means and said negative terminal, means for interrupting the supply of ignition pulses to said second tube whereby'the conductive condition of each of said tubes is controlled, said tubes being alternately conductive for periods determined by the discharge times of the associated first and-second capacitors, said interrupting means comprising a fourth resistor, a diode having an anode connected to a point on the connection between said second pulse source and the control electrode of said second tube and a cathode .connected to oneend of said fourth resistor, the other end of said fourth resistor being connected to said negative terminal, and means connected to the cathode of said diode for controlling the conductive condition thereof.

4. A circuit arrangement comprising first and second gas discharge tubes each having an anode, a cathode and a control grid, said cathodes beingconnected together, means for supplying a direct voltage having arpositive polarity terminal and a negative polarity terminal, a first resistor connecting the anode of said first tube to said positive terminal, a second resistor connecting the anode of said second tube to said positive terminal, a third resistor connecting the common cathode connection to said negative terminal, means for deriving an output voltage across said first resistor, first ignition pulse supplying means, a first capacitor connected in series circuit arrangement with said first pulse means between the con- .trol electrode of said first tube and the anode of said tube and the anode of said first tube, said second pulse source being interposed between said second capacitor and said control grid, a second variable resistor connected between a point in said last-mentioned series circuit arrangement interposed between said second capacitor and said second pulse means and said negative terminal, means for interrupting the supply of ignition pulses to said second tube whereby the conductive condition of each of said tubes is controlled, said tubes being alternately conductive for periods determined by the discharge times of the associated first and second capacitors, said interrupting means comprising a fourth resistor, a diode having an anode connected to a point on the connection between said second pulse source and the control electrode of said second tube and a cathode connected to one end of said fourth resistor, the other end of said fourth resistor being connected to said negative terminal, and means connected to the cathode of said diode for controlling the conductive condition thereof, said control means comprising a third gas discharge tube having an anode, a cathode connected to the cathode of said diode and a control grid and means for supplying a direct positive voltage to the anode of said third tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,464,528 Rava Mar. 15, 1949 

